Embodiments of the present disclosure generally relate to physiological signal processing and, more particularly, to processing physiological signals to determine a stroke volume or cardiac output of a patient.
In cardiovascular physiology, stroke volume (SV) is the volume of blood pumped from one ventricle of the heart with each beat. SV is calculated using measurements of ventricle volumes from an echocardiogram (ECG) and subtracting the volume of the blood in the ventricle at the end of a beat (end-systolic volume) from the volume of blood just prior to the beat (called end-diastolic volume). Stroke volume is an important determinant of cardiac output, which is the product of stroke volume and heart rate. Because stroke volume decreases in certain conditions and disease states, stroke volume itself correlates with cardiac function.
Systems and methods have been used to measure stroke volume. For example, photoplethysmogram (PPG) systems have been used in connection with ECG systems to aid in determining SV by measuring pulse transit times from the pulse measurement by the ECG system and the pulse measurement by the PPG system. The PPG system performs a non-invasive, optical measurement that may be used to detect changes in blood volume within tissue, such as skin, of an individual.